U.S. patent application number 11/864382 was filed with the patent office on 2008-04-03 for imaging lens and camera apparatus.
Invention is credited to Taro ASAMI.
Application Number | 20080080065 11/864382 |
Document ID | / |
Family ID | 38829589 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080080065 |
Kind Code |
A1 |
ASAMI; Taro |
April 3, 2008 |
IMAGING LENS AND CAMERA APPARATUS
Abstract
An imaging lens is configured sequentially from the object side
by: a first lens having a meniscus shape where a convex surface is
directed to the object side; a second lens; and a positive third
lens in which an image-side surface is a convex surface. The first
lens, the second lens, and the third lens are configured by a
bi-aspherical plastic lens. The second lens is configured by a
bi-convex lens in which the absolute value of the radius of
curvature of the object-side surface is smaller than that of the
image-side surface. The third lens is a positive lens and a
meniscus lens in which a concave surface is directed to the object
side, and a convex surface is directed to the image side.
Inventors: |
ASAMI; Taro; (Saitama-shi,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
38829589 |
Appl. No.: |
11/864382 |
Filed: |
September 28, 2007 |
Current U.S.
Class: |
359/716 |
Current CPC
Class: |
G02B 13/0035 20130101;
G02B 9/12 20130101 |
Class at
Publication: |
359/716 |
International
Class: |
G02B 3/02 20060101
G02B003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2006 |
JP |
P 2006-268866 |
Claims
1. An imaging lens comprising: in order from an object side of the
imaging lens, a first lens of a negative lens having a meniscus
shape and having a convex surface on the object side thereof; a
second lens having at least one aspherical surface; an aperture
diaphragm; and a third lens of a positive lens having at least one
aspherical surface and having a convex surface on an image side
thereof, the imaging lens satisfying conditional expressions:
0<|f2/f3|<0.49 (1) 1.5<.nu.3/.nu.2 (2)
0.5<|f1/f23|<3.0 (3) wherein f1, f2, and f3 are focal lengths
of the first lens, the second lens and the third lens,
respectively, .nu.2, and .nu.3 are Abbe numbers of the second lens
and the third lens, respectively, and f23 is a composite focal
length of the second and third lenses.
2. The imaging lens according to claim 1, further satisfying
conditional expression: 0<L/f<10.0 (4) wherein L is a
distance between an apex of an object-side surface of the first
lens and an image plane of the imaging lens, and f is a focal
length of the imaging lens.
3. The imaging lens according to claim 1, wherein a material of
each of the first and third lenses has an Abbe number of 40 or
more, and a material of the second lens has an Abbe number of 40 or
less.
4. The imaging lens according to claim 1, further satisfying
conditional expression: R3/f<1.0 (6) wherein R3 is a radius of
curvature of an object-side surface of the second lens.
5. The imaging lens according to claim 1, further satisfying
conditional expression: D1/f<1 (7) wherein D1 is a distance
between the apex on the object side of the first lens and that on
the image side.
6. The imaging lens according to claim 1, further satisfying
conditional expression: 2<|R4/D3|<6 (9) wherein R4 is a
radius of curvature of an image-side surface of the second lens,
and D3 is a center thickness of the second lens.
7. The imaging lens according to claim 2, wherein a material of
each of the first and third lenses has an Abbe number of 40 or
more, and a material of the second lens has an Abbe number of 40 or
less.
8. The imaging lens according to claim 7, further satisfying
conditional expression: R3/f<1.0 (6) wherein R3 is a radius of
curvature of an object-side surface of the second lens.
9. The imaging lens according to claim 8, further satisfying
conditional expression: D1/f<1 (7) wherein D1 is a distance
between the apex on the object side of the first lens and that on
the image side.
10. The imaging lens according to claim 9, further satisfying
conditional expression: 2<|R4/D3|<6 (9) wherein R4 is a
radius of curvature of an image-side surface of the second lens,
and D3 is a center thickness of the second lens.
11. A camera apparatus comprising: an imaging lens according to
claim 1, and a solid-state imaging device that converts an optical
image formed by the imaging lens to an electrical signal.
12. An imaging lens comprising: in order from an object side of the
imaging lens, a first lens of a negative lens having at least one
surface aspherical surface and having a concave surface on an image
side thereof a second lens having at least one aspherical surface;
an aperture diaphragm; and a third lens of a positive lens having
at least one aspherical surface and having a convex surface on the
image side thereof, the imaging lens satisfying conditional
expressions: 0<|f2/f3|<0.49 (1) 1.5<.nu.3/.nu.2 (2)
0.5<|f1/f23|<3.0 (3) N1<1.80 (5) wherein f1, f2, and f3
are focal lengths of the first lens, the second lens and the third
lens, respectively, .nu.2, and .nu.3 are Abbe numbers of the second
lens and the third lens, respectively, N1 is a refractive index of
the first lens at the d-line, and f23 is a composite focal length
of the second and third lenses.
13. The imaging lens according to claim 12, wherein the first lens
has a convex surface on the object side thereof.
14. The imaging lens according to claim 12, further satisfying
conditional expression: 0<L/f<10.0 (4) wherein L is a
distance between an apex of an object-side surface of the first
lens and an image plane of the imaging lens, and f is a focal
length of the imaging lens.
15. The imaging lens according to claim 12, wherein a material of
each of the first and third lenses has an Abbe number of 40 or
more, and a material of the second lens has an Abbe number of 40 or
less.
16. The imaging lens according to claim 12, further satisfying
conditional expression: R3/f<1.0 (6) wherein R3 is a radius of
curvature of an object-side surface of the second lens.
17. The imaging lens according to claim 12, further satisfying
conditional expression: D1/f<1 (7) wherein D1 is a distance
between the apex on the object side of the first lens and that on
the image side.
18. The imaging lens according to claim 12, further satisfying
conditional expression: 2<|R4/D3|<6 (9) wherein R4 is a
radius of curvature of an image-side surface of the second lens,
and D3 is a center thickness of the second lens.
19. The imaging lens according to claim 13, further satisfying
conditional expression: 0<L/f<10.0 (4) wherein L is a
distance between an apex of an object-side surface of the first
lens and an image plane of the imaging lens, and f is a focal
length of the imaging lens.
20. The imaging lens according to claim 19, wherein a material of
each of the first and third lenses has an Abbe number of 40 or
more, and a material of the second lens has an Abbe number of 40 or
less.
21. The imaging lens according to claim 20, further satisfying
conditional expression: R3/f<1.0 (6) wherein R3 is a radius of
curvature of an object-side surface of the second lens.
22. The imaging lens according to claim 21, further satisfying
conditional expression: D1/f<1 (7) wherein D1 is a distance
between the apex on the object side of the first lens and that on
the image side.
23. The imaging lens according to claim 22, further satisfying
conditional expression: 2<|R4/D3|<6 (9) wherein R4 is a
radius of curvature of an image-side surface of the second lens,
and D3 is a center thickness of the second lens.
24. A camera apparatus comprising: an imaging lens according to
claim 12, and a solid-state imaging device that converts an optical
image formed by the imaging lens to an electrical signal.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an imaging lens which is
suitably used in a vehicle camera, a surveillance camera, a camera
for a portable telephone, or the like, and which forms an optical
image on a solid-state imaging device, and also relates to a camera
apparatus comprising the lens.
[0003] 2. Description of Related Art
[0004] A vehicle camera for imaging the surrounding of a vehicle is
known (for example, see JP-A-2006-168683). Such vehicle cameras
include: an out-vehicle camera which is disposed outside a vehicle,
and which images, for example, a blind zone of the driver's vision
to assist the driving operation; and an in-vehicle camera which
images a field of view identical with the driver's vision field in
order to record the status of occurrence of a traffic accident or
the like. In accordance with enhancement of performance and cost
reduction of a solid-state imaging device, recently, vehicles
having a vehicle camera are becoming popular.
[0005] Among imaging lenses in the background art, an imaging lens
disclosed in JP-A-2001-337268 comprises a first lens which is a
meniscus lens having a negative refractive power, and positive
second and third lenses, sequentially from the object side. All the
surfaces other than the object-side surface of the first lens are
formed as an aspherical surface, so that excellent telecentricity
and a wide field angle are realized. An imaging lens disclosed in
JP-A-2005-181596 comprises a first lens which is a meniscus
spherical glass lens having a negative refractive power, and second
and third lenses which are aspherical plastic lenses having
positive refractive powers, and realizes the brightness of F 2.6
and a wide field angle of 80 degree or more. An imaging lens
disclosed in JP-A-2005-321742 is configured by three plastic lenses
in which the surface closest to the object side is a spherical
surface, and the other surfaces are formed as an aspherical
surface, and realizes the brightness of F 2.96 and a wide field
angle of 150 degree or more. Endoscope imaging lenses disclosed in
Japanese Patent No. 3206930 and JP-A-10-170821 comprise a
plano-concave lens and two positive lenses sequentially from the
object side, and simultaneously realize excellent telecentricity
and compactness.
[0006] However, the imaging lenses disclosed in JP-A-2001-337268,
JP-A-2005-181596 and JP-A-2005-321742 are insufficient in
miniaturization. The imaging lens disclosed in Japanese Patent No.
3206930 uses high-refractive index glass as the first lens, and
hence has a disadvantage that the cost is high. The imaging lens
disclosed in JP-A-10-170821 has the F-number of 3.8 or more, and
hence is dark. Therefore, the imaging lens is not suitable for use
in a vehicle camera, surveillance camera, or the like which is not
always used in an environment of adequate brightness.
SUMMARY OF THE INVENTION
[0007] An object of an illustrative, non-limiting embodiment of the
invention is to provide an imaging lens which can maintain
excellent optical performance, and which is reduced in size,
weight, and cost, and also a camera comprising the imaging
lens.
[0008] According to an aspect of the invention, there is provided
an imaging lens including sequentially from the object side, a
first lens of a negative lens having a meniscus shape and having a
convex surface on the object side; a second lens having at least
one aspherical surface; and a third lens of a positive lens having
a convex surface on the image side and having at least one
aspherical surface. An aperture diaphragm is disposed between the
second lens and the third lens, and the imaging lens satisfies
following conditional expressions:
0<|f2/f3|<0.49 (1)
1.5<.nu.3/.nu.2 (2)
0.5<|f1/f23|<3.0 (3)
where f1, f2, and f3 are focal lengths of the first lens, the
second lens and the third lens, respectively, .nu.2, and .nu.3 are
Abbe numbers of the second lens and the third lens, respectively,
and f23 is a composite focal length of the second and third
lenses.
[0009] When exceeding the upper limit of conditional expression
(1), it is possible to obtain a long exit pupil distance, but it is
difficult to achieve miniaturization and increased wide angle of
the imaging lens. When failing to satisfy the range of conditional
expression (2), it is difficult to sufficiently correct lateral
chromatic aberration. When exceeding the upper limit of conditional
expression (3), it is difficult to extend the filed of view, and at
the same time the curvature of field is increased. When being below
the lower limit of conditional expression (3), the field of view
can be increased, but coma aberration is increased and the image
quality of a peripheral portion of an image surface is
impaired.
[0010] In order to sufficiently correct the curvature of field,
distortion, and the like, at least one surface of the first lens
may be formed as an aspherical surface. In order to further correct
the curvature of field and coma aberration, the first lens may be
configured by a lens in which the both surfaces are formed as an
aspherical surface. In order to obtain an excellent image in which
chromatic aberration of magnification is corrected, the second lens
may be configured by a material having the Abbe number of 40 or
less, and the first and third lenses may be configured by a
material having the Abbe number of 40 or more.
[0011] Furthermore, the imaging lens may further satisfy a
following conditional expression:
0<L/f<10.0 (4)
where L is a distance between an apex of the object-side surface of
the first lens and an image plane of the imaging lens, and f is an
overall focal length. This configuration is suitable for reducing
the size of the imaging lens. Preferably, the imaging lens may
satisfy a following conditional expression:
0<L/f<5.50 (4')
[0012] By the satisfying the conditional expression (4'), the wide
angle of the imaging lens can be held and reduction of the size of
the imaging lens can be achieved.
[0013] According to an aspect of the invention, there is provided
an imaging lens including sequentially from the object side, a
first lens of a negative lens having at least one aspherical
surface having a concave surface on the image side; a second lens
having at least one aspherical surface; and a third lens of a
positive lens having a convex surface on the image side and having
at least one aspherical surface. An aperture diaphragm is disposed
between the second lens and the third lens, and the imaging lens
satisfies following conditional expressions:
0<|f2/f3|<0.49 (1)
1.5<.nu.3/.nu.2 (2)
0.5<|f1/f23|<3.0 (3)
N1<1.80 (5)
where f1, f2, and f3 are focal lengths of the first lens, the
second lens and the third lens, respectively, .nu.2, and .nu.3 are
Abbe numbers of the second lens and the third lens, respectively N1
is a refractive index of the first lens at the d-line, and f23 is a
composite focal length of the second and third lenses.
[0014] In the imaging lens, an object-side surface of the first
lens may be a convex surface.
[0015] The imaging lens may satisfy:
R3/f<1.0 (6)
where R3 is a radius of curvature of the object-side surface of the
second lens.
[0016] The imaging lens may satisfy:
D1/f<1 (7)
where D1 is the distance (center thickness) between the apex on the
object side of the first lens and that on the image side, whereby
the size of the imaging lens can be prevented from being
increased.
[0017] Preferably, the imaging lens further satisfy:
0.5<D1/f<0.8 (8).
[0018] From the viewpoint of suppressing the increase of chromatic
aberration, the imaging lens may satisfy:
2<|R4/D3|<6 (9)
where R4 is the radius of curvature of the image-side surface of
the second lens, and D3 is the center thickness of the second lens.
Furthermore, the imaging lens may satisfy:
2.5<|R4/D3|<4.2 (10).
[0019] The imaging lens satisfy:
1.5<(D1+D3+D6)/f<4 (11)
where D6 is the center thickness of the third lens, and further may
satisfy:
2<(D1+D3+D6)/f<3 (12).
[0020] When exceeding the upper limit of the formula (11), the back
focus is shortened or the lens is increased in size. When being
below the lower limit of the formula (11), the focal length is
shortened, and the angle is hardly broadened.
[0021] According to an aspect of the invention, there is provided a
camera apparatus including the imaging lens as above-mentioned, and
a solid-state imaging device which converts an optical image formed
by the imaging lens to an electric signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The features of the invention will appear more fully upon
consideration of the exemplary embodiment of the invention, which
are schematically set forth in the drawings, in which:
[0023] FIG. 1 is an optical path diagram of Example 1;
[0024] FIG. 2 is a section view showing the lens configuration of
Example 1;
[0025] FIG. 3 is an aberration diagram of Example 1;
[0026] FIG. 4 is a section view showing the lens configuration of
Example 2;
[0027] FIG. 5 is an aberration diagram of Example 2;
[0028] FIG. 6 is a section view showing the lens configuration of
Example 3;
[0029] FIG. 7 is an aberration diagram of Example 3;
[0030] FIG. 8 is a section view showing the lens configuration of
Example 4;
[0031] FIG. 9 is an aberration diagram of Example 4;
[0032] FIG. 10 is a section view showing the lens configuration of
Example 5;
[0033] FIG. 11 is an aberration diagram of Example 5;
[0034] FIG. 12 is a section view showing the lens configuration of
Example 6;
[0035] FIG. 13 is an aberration diagram of Example 6; and
[0036] FIG. 14 is a diagram showing vehicle cameras.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0037] Although the invention will be described below with
reference to exemplary embodiments thereof, the following exemplary
embodiments and modifications do not restrict the invention.
[0038] According to an exemplary embodiment of the invention, it is
possible to realize an imaging lens which has the F-number of 2.8,
and hence is bright, in which curvature of field is sufficiently
corrected, and a wide field angle of a diagonal field angle of 90
degree or more is obtained, which is suitable for use in a vehicle
camera, a surveillance camera, or the like, and which has a reduced
size and high performance.
[0039] Referring to FIG. 14, a vehicle 1 includes: an out-vehicle
camera 2 for imaging a blind zone in the lateral side on the
passenger side; an out-vehicle camera 3 for imaging a blind zone in
rear of the vehicle 1; and an in-vehicle camera 4 attached to the
rear side of a rear-view mirror, and for imaging a field of view
identical with the driver's vision field. Each of the out-vehicle
camera 2, the out-vehicle camera 3, and the in-vehicle camera 4
comprises an imaging lens 10, and a solid-state imaging device S1
configured by a CCD image sensor. Hereinafter, examples of the
imaging lens 10 will be described.
Example 1
[0040] Referring to FIGS. 1 and 2, the imaging lens 10 includes
sequentially from the object side a first lens 11, a second lens
12, and a third lens 13. Each of the first to third lenses 11 to 13
is configured by a bi-aspherical plastic lens having aspherical
surfaces which are rotationally symmetric about the optical axis.
The first lens 11 has a negative refractive power and has a
meniscus shape where a convex surface is on the object side, a
concave surface is on the image side, and the absolute value of the
radius of curvature of the image-side surface is smaller than that
of the object-side surface. A light shielding film 11a is disposed
on a region outside the image-side concave surface of the first
lens 11. The light shielding film 11a prevents light from entering
from the outside of the effective diameter, and a ghost image from
appearing on the image plane. The light shielding film 11a is a
layer of an opaque coating composition which is disposed outside
the effective diameter of the first lens 11. Alternatively, an
opaque plate member may be disposed on the rear surface of the
first lens 11. The light shielding film 11a is not restricted to be
disposed in rear of the first lens 11, and may be disposed between
other lenses depending on the occasion.
[0041] The second lens 12 has a bi-convex shape where each of the
object-side and image-side surfaces is a convex surface, and the
absolute value of the radius of curvature of the object side
surface is smaller than that of the image-side surface. The third
lens 13 has a positive meniscus shape where a concave surface is on
the object side, a convex surface is on the image side, and the
absolute value of the radius of curvature of the image-side convex
surface is smaller than that of the object-side surface. An
aperture diaphragm ST is disposed between the second lens 12 and
the third lens 13. A light receiving surface of the solid-state
imaging device S1 such as a CCD image sensor or a CMOS image sensor
is positioned in the image plane. A cover glass for the solid-state
imaging device S1, and filters such as an infrared blocking filter
are disposed as a plane parallel plate PP between the third lens 13
and the image surface. Table 1 below shows lens data of the imaging
lens 10, Table 2 shows aspherical coefficients of the first to
third lenses 11 to 13, and Table 3 shows design specification of
the imaging lens 10. The aspherical surfaces, and also those of the
other examples are based on the following aspherical expression
where KA is a conical constant of an aspherical surface, Bi is an
i-th order aspherical coefficient, C is the reciprocal of a
paraxial radius of curvature, and Y is the height from the optical
axis.
Z = CY 2 1 + 1 - KA * C 2 Y 2 + B i Y i ##EQU00001## i = 3 to n
##EQU00001.2##
TABLE-US-00001 TABLE 1 Example 1 Surface Number R D N .nu.d 1 12.25
1.21 1.50869 56 2 0.88 1.60 3 1.52 1.50 1.58362 30.2 4 -6.00 0.20
ST 5 0.00 0.62 6 -60.80 1.63 1.50869 56 7 -2.30 0.50 8 0.00 0.50
1.5168 64.2 9 0.00 0.99 Image 0.00 0.00
TABLE-US-00002 TABLE 2 Aspherical Coefficent Surface Number KA B3
B4 B5 B6 B7 1 -6.71E+02 3.75E-02 -3.15E-02 3.76E-03 6.79E-03
-3.28E-03 2 1.09E-01 -2.72E-02 1.43E-02 -2.51E-02 5.94E-03 3.20E-03
3 2.35E-01 4.33E-03 1.13E-03 -7.67E-03 -9.19E-03 1.63E-02 4
-1.95E+04 -1.72E-01 1.78E-01 7.44E-02 -9.49E-02 -8.44E-02 6
-8.61E+11 9.75E-02 -3.44E-01 9.38E-02 1.47E-01 1.79E-01 7 -7.28E+01
-2.84E-01 1.72E-01 -4.37E-02 1.21E-02 -2.23E-02 Surface Number B8
B9 B10 B11 B12 B13 1 4.39E-04 3.17E-05 -8.52E-06 -1.36E-08
-1.37E-08 -5.79E-09 2 -2.08E-04 4.82E-03 -1.34E-03 6.59E-04
2.79E-05 -1.40E-04 3 4.98E-03 -1.05E-02 -8.12E-04 1.08E-03 1.11E-04
-4.51E-04 4 -2.79E-02 -2.43E-01 1.63E-01 1.49E-01 1.67E-01 9.59E-02
6 -1.54E-01 -4.57E-01 3.08E-01 -1.04E-01 -1.33E-01 -7.82E-02 7
6.12E-03 5.48E-03 -3.44E-03 4.53E-04 1.72E-04 1.43E-04 Surface
Number B14 B15 B16 B17 B18 B19 B20 1 -1.73E-09 -2.89E-10 6.39E-11
-1.70E-11 -1.39E-12 1.76E-12 1.60E-12 2 -1.73E-04 -1.42E-04
-9.67E-05 -3.24E-05 -6.85E-06 9.29E-06 1.82E-05 3 -5.82E-04
-3.81E-04 2.85E-05 -1.62E-04 -3.19E-05 6.82E-05 1.29E-04 4
-1.57E-02 -1.69E-01 -2.25E-01 -1.57E-01 2.57E-01 2.80E-01 -1.81E-01
6 1.41E-01 4.33E-01 7.66E-01 -1.80E-01 -1.08E+00 -1.29E+00 1.51E+00
7 -2.90E-05 -1.11E-04 -1.24E-04 2.69E-05 2.09E-05 1.03E-05
-1.10E-06
TABLE-US-00003 TABLE 3 f 1.82 f1 -1.93 f2 2.22 f3 4.64 f23 2.50
2.omega. 103.4 L(in Air) 8.57 Fno 2.8
[0042] In the tables, R indicates the radius of curvature of a
spherical surface of a lens element, or the curvature of a
reference surface of an aspherical surface, D indicates the surface
separation or the air space, N indicates the refractive index at
the d-line (wavelength=587.6 mm), and .nu. indicates the Abbe
number at the d-line. In the tables, f indicates the focal length
(mm) of the whole system, f1 indicates the focal length (mm) of the
first lens 11, f2 indicates the focal length (mm) of the second
lens 12, f3 indicates the focal length (mm) of the third lens 13,
f23 indicates the composite focal length (mm) of the second lens 12
and the third lens 13, 2.omega. indicates the diagonal field angle
(.degree.), L indicates the distance (mm) between the apex of the
object-side surface and the image surface, and Fno indicates the
F-number. These are similarly applicable also to the other examples
which will be described later.
[0043] In the imaging lens 10, |f2/f3|=0.48, and
0<|f2/f3|<0.49 (1)
is satisfied. Moreover, .nu.3/.nu.2=1.85, and
1.5<.nu.3/.nu.2 (2)
is satisfied. Moreover, |f1/f23|=0.77, and
0.5<|f1/f23|<3.0 (3)
is satisfied. Moreover, L/f=4.70, and
0<L/f<10.0 (4)
is satisfied. Moreover, N1=1.51, and
N1<1.80 (5)
is satisfied. Moreover, R3/f=0.83, and
R3/f<1.0 (6)
is satisfied. Moreover, D1/f=0.66, and both expressions:
D1/f<1 (7)
0.5<D1/f<0.8 (8)
are satisfied. Moreover, R4/D3=-4.00, and both expressions:
2<|R4/D3|<6 (9)
2.5<|R4/D3|<4.2 (10)
are satisfied. Moreover, (D1+D3+D6)/f=2.38, and both
expressions:
1.5<(D1+D3+D6)/f<4 (11)
2<(D1+D3+D6)/f<3 (12)
are satisfied.
Example 2
[0044] Referring to FIG. 4, an imaging lens 20 includes
sequentially from the object side a first lens 21, a second lens
22, and a third lens 23. Each of the first to third lenses 21 to 23
is configured by a bi-aspherical plastic lens. The first lens 21
has a negative refractive power and has a meniscus shape where a
convex surface is on the object side, a concave surface is on the
image side, and the absolute value of the radius of curvature of
the image-side concave surface is smaller than that of the
object-side surface. The second lens 22 has a bi-convex shape where
each of the object and image side surfaces is a convex surface, and
the absolute value of the radius of curvature of the object-side
surface is smaller than that of the image-side surface. The third
lens 23 has a positive refractive power and has a meniscus shape
where a concave surface is on the object side, a convex surface is
on the image side, and the absolute value of the radius of
curvature of the image-side convex surface is smaller than that of
the object-side surface. An aperture diaphragm ST is disposed
between the second lens 22 and the third lens 23. A plane parallel
plate PP is disposed between the third lens 23 and the image plane.
Table 4 shows lens data of the imaging lens 20, Table 5 shows
aspherical coefficients of the surfaces, and Table 6 shows design
specification of the imaging lens.
TABLE-US-00004 TABLE 4 Example 2 Surface Number R D n .nu.d 1 8.60
1.21 1.50869 56 2 0.88 1.55 3 1.52 1.52 1.58362 30.2 4 -4.00 0.20
ST 5 0.00 0.49 6 -60.80 1.91 1.50869 56 7 -2.30 0.50 8 0.00 0.50
1.5168 64.2 9 0.00 0.55 Image 0.00 0.00
TABLE-US-00005 TABLE 5 Aspherical Coeffcient Surface Number KA B3
B4 B5 B6 B7 1 -7.27E+02 4.05E-02 -3.17E-02 3.64E-03 6.77E-03
-3.29E-03 2 8.49E-02 -4.70E-02 4.72E-03 -1.63E-02 7.32E-03 1.86E-03
3 3.35E-02 1.54E-02 -7.06E-03 -2.26E-02 -6.73E-03 1.83E-02 4
-2.78E+03 -1.88E-01 1.03E-01 2.33E-02 -5.42E-02 2.54E-02 6
-8.61E+11 1.05E-01 -3.25E-01 4.45E-02 3.82E-02 1.25E-01 7 -7.77E+01
-2.92E-01 2.05E-01 -2.91E-02 7.97E-03 -2.78E-02 Surface Number B8
B9 B10 B11 B12 B13 1 4.39E-04 3.17E-05 -8.53E-06 -1.37E-08
-1.31E-08 -5.29E-09 2 -1.63E-03 4.03E-03 -1.64E-03 6.00E-04
1.30E-04 -1.97E-05 3 5.31E-03 -1.11E-02 -1.57E-03 6.43E-04
-5.58E-07 -3.45E-04 4 7.51E-02 -2.16E-01 9.19E-02 1.01E-02 1.63E-02
-1.12E-03 6 -6.03E-02 -2.63E-01 5.09E-01 -1.68E-02 -4.38E-01
-5.85E-01 7 3.27E-03 4.49E-03 -3.34E-03 8.17E-04 5.37E-04 3.00E-04
Surface Number B14 B15 B16 B17 B18 B19 B20 1 -1.45E-09 -1.66E-10
1.08E-10 -5.04E-12 -1.44E-14 6.33E-13 4.57E-13 2 -7.85E-05
-7.75E-05 -5.96E-05 -1.65E-05 -5.32E-06 2.09E-06 6.45E-06 3
-4.08E-04 -2.40E-04 7.93E-05 -1.89E-04 -9.67E-05 2.71E-05 1.62E-04
4 -4.00E-03 -4.39E-02 -6.83E-03 1.82E-03 1.01E-01 9.96E-02
-8.39E-02 6 -4.37E-01 4.39E-02 8.64E-01 5.90E-01 2.67E-01 -2.80E-01
-3.64E-01 7 2.97E-05 -7.69E-05 -1.46E-04 -3.05E-06 -5.86E-07
3.00E-06 7.64E-06
TABLE-US-00006 TABLE 6 f 1.77 f1 -2.02 f2 2.08 f3 4.63 f23 2.44
2.omega. 105.6 L(in Air) 8.27 Fno 2.8
[0045] In the imaging lens 20, |f2/f3|=0.45, and
0<|f2/f3|<0.49 (1)
is satisfied. Moreover, .nu.3/.nu.2=1.85, and
1.5<.nu.3/.nu.2 (2)
is satisfied. Moreover, |f1/f23|=0.83, and
0.5<|f1/f23|<3.0 (3)
is satisfied. Moreover, L/f=4.67, and
0<L/f<10.0 (4)
is satisfied. Moreover, N1=1.51, and
N1<1.80 (5)
is satisfied. Moreover, R3/f=0.86, and
R3/f<1.0 (6)
is satisfied. Moreover, D1/f=0.68, and both expressions:
D1/f<1 (7)
0.5<D1/f<0.8 (8)
are satisfied. Moreover, R4/D3=-2.63, and both expressions:
2<|R4/D3|<6 (9)
2.5<|R4/D3|<4.2 (10)
are satisfied. Moreover, (D1+D3+D6)/f=2.62, and both
expressions:
1.5<(D1+D3+D6)/f<4 (11)
2<(D1+D3+D6)/f<3 (12)
are satisfied.
Example 3
[0046] Referring to FIG. 6, an imaging lens 30 includes
sequentially from the object side a first lens 31, a second lens
32, and a third lens 33. Each of the first to third lenses 31 to 33
is configured by a bi-aspherical plastic lens. The first lens 31
has a negative refractive power and a meniscus shape where a convex
surface is on the object side, a concave surface is on the image
side, and the absolute value of the radius of curvature of the
image-side concave surface is smaller than that of the object-side
convex surface. The second lens 32 has a bi-convex shape where each
of the object and image side surfaces is a convex surface, and the
absolute value of the radius of curvature of the object-side
surface is smaller than that of the image-side surface. The third
lens 33 has a positive refractive power and a meniscus shape where
a concave surface is on the object side, a convex surface is on the
image side, and the absolute value of the radius of curvature of
the image-side convex surface is smaller than that of the
object-side surface. An aperture diaphragm ST is disposed between
the second lens 32 and the third lens 33. A plane parallel plate PP
is disposed between the third lens 33 and the image plane. Table 7
shows lens data of the imaging lens 30, Table 8 shows aspherical
coefficients of the surfaces, and Table 9 shows design
specification of the imaging lens.
TABLE-US-00007 TABLE 7 Example 3 Surface Number R D n .nu.d 1 8.60
1.21 1.50869 58 2 0.88 1.62 3 1.52 1.52 1.58362 30.2 4 -4.00 0.20
ST 5 0.00 0.51 6 -60.80 1.92 1.50869 56 7 -3.00 0.50 8 0.00 0.50
1.5168 64.2 9 0.00 0.59 Image 0.00 0.00
TABLE-US-00008 TABLE 8 Aspherical Coefficient Surface Number KA B3
B4 B5 B6 B7 1 -9.02E+02 4.02E-02 -3.17E-02 3.64E-03 6.77E-03
-3.29E-03 2 8.69E-02 -4.30E-02 5.67E-03 -1.63E-02 7.25E-03 1.81E-03
3 3.22E-02 1.53E-02 -7.12E-03 -2.25E-02 -6.56E-03 1.84E-02 4
-2.71E+03 -1.89E-01 1.03E-01 2.33E-02 -5.43E-02 2.52E-02 6
-8.61E+11 1.04E-01 -3.26E-01 4.44E-02 4.05E-02 1.29E-01 7 -1.19E+02
-2.79E-01 2.06E-01 -3.09E-02 7.08E-03 -2.80E-02 Surface Number B8
B9 B10 B11 B12 B13 1 4.38E-04 3.17E-05 -8.53E-06 -1.60E-08
-1.37E-08 -5.45E-09 2 -1.66E-03 4.02E-03 -1.65E-03 5.97E-04
1.27E-04 -2.13E-05 3 5.37E-03 -1.11E-02 -1.57E-03 6.24E-04
-2.55E-05 -3.71E-04 4 7.49E-02 -2.16E-01 9.14E-02 9.57E-03 1.57E-02
-1.84E-03 6 -5.72E-02 -2.62E-01 5.07E-01 -2.22E-02 -4.47E-01
-5.95E-01 7 3.24E-03 4.52E-03 -3.30E-03 8.42E-04 5.52E-04 3.08E-04
Surface Number B14 B15 B16 B17 B18 B19 B20 1 -1.49E-09 -1.76E-10
1.06E-10 -5.52E-12 -7.41E-14 6.46E-13 4.72E-13 2 -7.96E-05
-7.83E-05 -6.02E-05 -1.70E-05 -5.63E-06 1.87E-06 6.29E-06 3
-4.30E-04 -2.58E-04 6.56E-05 -1.99E-04 -1.03E-04 2.36E-05 1.61E-04
4 -4.76E-03 -4.46E-02 -7.40E-03 1.58E-03 1.01E-01 1.00E-01
-8.41E-02 6 -4.49E-01 3.15E-02 8.53E-01 5.82E-01 2.65E-01 -2.73E-01
-3.44E-01 7 3.39E-05 -7.51E-05 -1.45E-04 -3.04E-06 -8.04E-07
2.73E-6 7.38E-06
TABLE-US-00009 TABLE 9 f 1.87 f1 -2.02 f2 2.08 f3 6.11 f23 2.36
2.omega. 105.7 L(in Air) 8.40 Fno 2.8
[0047] In the imaging lens 30, |f2/f3|=0.34, and
0<|f2/f3|<0.49 (1)
is satisfied. Moreover, .nu.3/.nu.2=1.85, and
1.5<.nu.3/.nu.2 (2)
is satisfied. Moreover, |f1/f23|=0.86, and
0.5<|f1/f23|<3.0 (3)
is satisfied. Moreover, L/f=4.50, and
0<L/f<10.0 (4)
is satisfied. Moreover, N1=1.51, and
N1<1.80 (5)
is satisfied. Moreover, R3/f=0.81, and
R3/f<1.0 (6)
is satisfied. Moreover, D1/f=0.65, and both expressions:
D1/f<1 (7)
0.5<D1/f<0.8 (8)
are satisfied. Moreover, R4/D3=-2.62, and both expressions:
2<|R4/D3|<6 (9)
2.5<|R4/D3|<4.2 (10)
are satisfied. Moreover, (D1+D3+D6)/f=2.49, and both
expressions:
1.5<(D1+D3+D6)/f<4 (11)
2<(D1+D3+D6)/f<3 (12)
are satisfied.
Example 4
[0048] Referring to FIG. 8, an imaging lens 40 includes
sequentially from the object side a first lens 41, a second lens
42, and a third lens 43. Each of the first to third lenses 41 to 43
is configured by a bi-aspherical plastic lens. The first lens 41
has a negative refractive power and a meniscus shape where a convex
surface is on the object side, a concave surface is on the image
side, and the absolute value of the radius of curvature of the
image-side concave surface is smaller than that of the object-side
surface. The second lens 42 has a bi-convex shape where each of the
object and image side surfaces is a convex surface, and the
absolute value of the radius of curvature of the object-side convex
surface is smaller than that of the image-side surface. The third
lens 43 has a positive refractive power and a meniscus shape where
a concave surface is on the object side, a convex surface is on the
image side, and the absolute value of the radius of curvature of
the image-side convex surface is smaller than that of the
object-side surface. An aperture diaphragm ST is disposed between
the second lens 42 and the third lens 43. A plane parallel plate PP
is disposed between the third lens 43 and the image plane. Table 10
shows lens data of the imaging lens 40, Table 11 shows aspherical
coefficients of the surfaces, and Table 12 shows design
specification of the imaging lens.
TABLE-US-00010 TABLE 10 Example 4 Surface Number R D n .nu.d 1
10.22 1.21 1.50869 56 2 0.93 1.81 3 1.63 1.52 1.58362 30.2 4 -4.00
0.20 ST 5 0.00 0.53 6 -60.80 1.94 1.50869 56 7 -3.10 0.50 8 0.00
0.50 1.5168 64.2 9 0.00 0.66 Image 0.00 0.00
TABLE-US-00011 TABLE 11 Aspherical Coefficient Surface Number KA B3
B4 B5 B6 B7 1 -1.51E+03 3.97E-02 -3.17E-02 3.64E-03 6.77E-03
-3.29E-03 2 9.49E-02 -3.42E-02 8.29E-03 -1.60E-02 7.15E-03 1.71E-03
3 2.55E-02 1.54E-02 -7.32E-03 -2.25E-02 -6.32E-03 1.86E-02 4
-2.43E+03 -1.91E-01 1.02E-01 2.34E-02 -5.37E-02 2.55E-02 6
-8.61E+11 1.06E-01 -3.23E-01 4.83E-02 4.47E-02 1.32E-01 7 -1.52E+02
-2.69E-01 2.05E-01 -3.34E-02 6.34E-03 -2.80E-02 Surface Number B8
B9 B10 B11 B12 B13 1 4.39E-04 3.17E-05 -8.53E-06 -1.57E-08
-1.34E-08 -5.33E-09 2 -1.71E-03 3.99E-03 -1.66E-03 5.94E-04
1.28E-04 -1.98E-05 3 5.49E-03 -1.11E-02 -1.63E-03 5.40E-04
-1.18E-04 -4.57E-04 4 7.41E-02 -2.19E-01 8.71E-02 3.51E-03 8.66E-03
-8.75E-03 6 -5.54E-02 -2.61E-01 5.09E-01 -1.69E-02 -4.36E-01
-5.79E-01 7 3.38E-03 4.63E-03 -3.24E-03 8.75E-04 5.66E-04 3.13E-04
Surface Number B14 B15 B16 B17 B18 B19 B20 1 -1.45E-09 -1.58E-10
1.12E-10 -3.90E-12 2.54E-13 6.47E-13 4.23E-13 2 -7.80E-05 -7.71E-05
-5.92E-05 -1.63E-05 -5.15E-06 2.19E-06 6.50E-06 3 -5.04E-04
-3.18E-04 2.04E-05 -2.32E-04 -1.25E-04 9.63E-06 1.53E-04 4
-9.68E-03 -4.48E-02 3.74E-04 2.04E-02 1.31E-01 1.29E-01 -1.12E-01 6
-4.28E-01 5.40E-02 8.71E-01 5.87E-01 2.49E-01 -3.18E-01 -4.15E-01 7
3.49E-05 -7.53E-05 -1.46E-04 -3.54E-06 -1.13E-06 2.55E-06
7.31E-06
TABLE-US-00012 TABLE 12 f 1.84 f1 -2.10 f2 2.19 f3 6.32 f23 2.44
2.omega. 109.6 L(in Air) 8.69 Fno 2.8
[0049] In the imaging lens 40, |f2/f3|=0.35, and
0<|f2/f3|<0.49 (1)
is satisfied. Moreover, .nu.3/.nu.2=1.85, and
1.5<.nu.3/.nu.2 (2)
is satisfied. Moreover, |f1/f23|=0.86, and
0.5<|f1/f23|<3.0 (3)
is satisfied. Moreover, L/f=4.73, and
0<L/f<10.0 (4)
is satisfied. Moreover, N1=1.51, and
N1<1.80 (5)
is satisfied. Moreover, R3/f=0.89, and
R3/f<1.0 (6)
is satisfied. Moreover, D1/f=0.66, and both expressions:
D1/f<1 (7)
0.5<D1/f<0.8 (8)
are satisfied. Moreover, R4/D3=-2.62, and both expressions:
2<|R4/D3|<6 (9)
2.5<|R4/D3|<4.2 (10)
are satisfied. Moreover, (D1+D3+D6)/f=2.55, and both
expressions:
1.5<(D1+D3+D6)/f<4 (11)
2<(D1+D3+D6)/f<3 (12)
are satisfied.
Example 5
[0050] Referring to FIG. 10, an imaging lens 50 includes
sequentially from the object side a first lens 51, a second lens
52, and a third lens 53. Each of the first to third lenses 51 to 53
is configured by a bi-aspherical plastic lens. The first lens 51
has a negative refractive power and has a meniscus shape where a
convex surface is on the object side, and a concave surface is on
the image side. The second lens 52 has a bi-convex shape where each
of the object and image side surfaces is a convex surface, and the
absolute value of the radius of curvature of the object-side convex
surface is smaller than that of the image-side surface. The third
lens 53 has a positive refractive power and a meniscus shape where
a concave surface is on the object side, a convex surface is on the
image side, and the absolute value of the radius of curvature of
the image-side convex surface is smaller than that of the
object-side surface. An aperture diaphragm ST is disposed between
the second lens 52 and the third lens 53. A plane parallel plate PP
is disposed between the third lens 53 and the image plane. Table 13
shows lens data of the imaging lens 50, Table 14 shows aspherical
coefficients of the surfaces, and Table 15 shows design
specification of the imaging lens.
TABLE-US-00013 TABLE 13 Example 5 Surface Number R D n .nu.d 1
100.00 1.21 1.50869 56 2 0.93 1.98 3 1.63 1.53 1.58362 30.2 4 -4.00
0.20 ST 5 0.00 0.50 6 -60.80 1.97 1.50869 56 7 -3.44 0.50 8 0.00
0.50 1.5168 64.2 9 0.00 0.70 Image 0.00 0.00
TABLE-US-00014 TABLE 14 Aspherical Coefficient Surface Number KA B3
B4 B5 B6 B7 1 -1.51E+03 3.97E-02 -3.17E-02 3.64E-03 6.77E-03
-3.29E-03 2 9.49E-02 -3.42E-02 8.29E-03 -1.60E-02 7.15E-03 1.71E-03
3 2.55E-02 1.54E-02 -7.32E-03 -2.25E-02 -6.32E-03 1.86E-02 4
-2.43E+03 -1.91E-01 1.02E-01 2.34E-02 -5.37E-02 2.55E-02 6
-8.61E+11 1.06E-01 -3.23E-01 4.83E-02 4.47E-02 1.32E-01 7 -1.52E+02
-2.69E-01 2.05E-01 -3.34E-02 6.34E-03 -2.80E-02 Surface Number B8
B9 B10 B11 B12 B13 1 4.39E-04 3.17E-05 -8.53E-06 -1.57E-08
-1.34E-08 -5.33E-09 2 -1.71E-03 3.99E-03 -1.66E-03 5.94E-04
1.28E-04 -1.98E-05 3 5.49E-03 -1.11E-02 -1.63E-03 5.40E-04
-1.18E-04 -4.57E-04 4 7.41E-02 -2.19E-01 8.71E-02 3.51E-03 8.66E-03
-8.75E-03 6 -5.54E-02 -2.61E-01 5.09E-01 -1.69E-02 -4.36E-01
-5.79E-01 7 3.38E-03 4.63E-03 -3.24E-03 8.75E-04 5.66E-04 3.13E-04
Surface Number B14 B15 B16 B17 B18 B19 B20 1 -1.45E-09 -1.58E-10
1.12E-10 -3.90E-12 2.54E-13 6.47E-13 4.23E-13 2 -7.80E-05 -7.71E-05
-5.92E-05 -1.63E-05 -5.15E-06 2.19E-06 6.50E-06 3 -5.04E-04
-3.18E-04 2.04E-05 -2.32E-04 -1.25E-04 9.63E-06 1.53E-04 4
-9.68E-03 -4.48E-02 3.74E-04 2.04E-02 1.31E-01 1.29E-01 -1.12E-01 6
-4.28E-01 5.40E-02 8.71E-01 5.87E-01 2.49E-01 -3.18E-01 -4.15E-01 7
3.49E-05 -7.53E-05 -1.46E-04 -3.54E-06 -1.13E-06 2.55E-06
7.31E-06
TABLE-US-00015 TABLE 15 f 1.65 f1 -1.85 f2 2.19 f3 7.06 f23 2.41
2.omega. 124 L(in Air) 8.92 Fno 2.8
[0051] In the imaging lens 50, |f2/f3=0.31, and
0<|f2/f3|<0.49 (1)
is satisfied. Moreover, .nu.3/.nu.2=1.85, and
1.5<.nu.3/.nu.2 (2)
is satisfied. Moreover, |f1/f23|=0.77, and
0.5<|f1/f23|<3.0 (3)
is satisfied. Moreover, L/f=5.40, and
0<L/f<10.0 (4)
is satisfied. Moreover, N1=1.51, and
N1<1.80 (5)
is satisfied. Moreover, R3/f=0.99, and
R3/f<1.0 (6)
is satisfied. Moreover, D1/f=0.73, and both expressions:
D1/f<1 (7)
0.5<D1/f<0.8 (8)
are satisfied. Moreover, R4/D3=-2.62, and both expressions:
2<|R4/D3|<6 (9)
2.5<|R4/D3|<4.2 (10)
are satisfied. Moreover, (D1+D3+D6)/f=2.85, and both
expressions:
1.5<(D1+D3+D6)/f<4 (11)
2<(D1+D3+D6)/f<3 (12)
are satisfied.
Example 6
[0052] Referring to FIG. 12, an imaging lens 60 includes
sequentially from the object side a first lens 61, a second lens
62, and a third lens 63. Each of the first to third lenses 61 to 63
is configured by a bi-aspherical plastic lens. The first lens 61
has a negative refractive power and has a meniscus shape where a
convex surface is on the object side, and a concave surface is on
the image side and the absolute value of the radius of curvature of
the image-side concave surface is smaller than that of the
object-side surface. The second lens 62 has a bi-convex shape where
each of the object and image side surfaces, and the absolute value
of the radius of curvature of the object-side convex surface is
smaller than that of the image-side surface. The third lens 63 has
a flat surface in the vicinity of the optical axis on the object
side, and a convex surface on the image side. An aperture diaphragm
ST is disposed between the second lens 62 and the third lens 63. A
plane parallel plate PP is disposed between the third lens 63 and
the image plane. Table 16 shows lens data of the imaging lens 60,
Table 17 shows aspherical coefficients of the surfaces, and Table
18 shows design specification of the imaging lens.
TABLE-US-00016 TABLE 16 Example 6 Surface Number R D n .nu.d 1 3.00
1.20 1.50869 66 2 1.00 1.69 3 1.52 1.50 1.58362 30.2 4 -5.00 0.20
ST 5 0.00 0.40 6 0.00 2.06 1.50869 56 7 -2.30 0.30 8 0.00 0.30
1.5168 64.2 9 0.00 0.31 Image 0.00 0.00
TABLE-US-00017 TABLE 17 Aspherical Coefficient Surface Number KA B3
B4 B5 B6 B7 1 -8.73E+00 3.57E-02 -3.16E-02 3.92E-03 6.84E-03
-3.27E-03 2 1.52E-01 -2.04E-02 2.64E-02 -2.10E-02 8.12E-03 3.85E-03
3 4.91E-02 3.84E-02 7.24E-04 -1.00E-02 -1.31E-02 1.56E-02 4
-7.90E+03 -1.81E-01 1.69E-01 7.10E-02 -9.73E-02 -8.92E-02 6
0.00E+00 9.71E-02 -4.20E-01 4.19E-02 1.40E-01 2.01E-01 7 -1.01E+02
-3.14E-01 1.40E-01 -5.09E-02 1.20E-02 -2.36E-02 Surface Number B8
B9 B10 B11 B12 B13 1 4.41E-04 3.17E-05 -8.63E-06 -7.09E-08
-3.99E-08 -1.39E-08 2 -2.45E-04 4.70E-03 -1.45E-03 6.23E-04
3.41E-05 -1.33E-04 3 4.56E-03 -1.03E-02 -1.10E-03 9.59E-04 1.98E-05
-5.51E-04 4 -3.99E-02 -2.48E-01 1.63E-01 1.73E-01 2.90E-01 1.79E-01
6 -1.30E-01 -4.13E-01 3.48E-01 -8.48E-02 -1.45E-01 -7.46E-02 7
5.00E-03 4.26E-03 -3.93E-03 3.11E-04 1.94E-04 3.23E-04 Surface
Number B14 B15 B16 B17 B18 B19 B20 1 -4.11E-09 -9.39E-10 -9.36E-11
-5.26E-11 -7.83E-12 5.56E-12 3.13E-12 2 -1.72E-04 -1.43E-04
-9.71E-05 -3.30E-05 -8.08E-06 8.05E-06 1.76E-05 3 -5.61E-04
-3.72E-04 -4.14E-05 -1.85E-04 -5.45E-05 3.15E-05 9.00E-05 4
1.80E-01 9.07E-02 1.24E-01 -6.00E-01 -1.04E+00 -2.98E+00 2.05E+00 6
1.09E-01 4.28E-01 7.46E-01 -2.16E-01 -1.08E+00 -1.28E+00 1.54E+00 7
6.32E-05 4.08E-05 -5.69E-05 3.72E-05 2.35E-05 7.10E-07
-9.82E-06
TABLE-US-00018 TABLE 18 f 2.21 f1 -3.68 f2 2.16 f3 4.50 f23 2.49
2.omega. 97.4 L(in Air) 7.84 Fno 2.8
[0053] In the imaging lens 60, |f2/f3=0.48, and
0<|f2/f3|<0.49 (1)
is satisfied. Moreover, .nu.3/.nu.2=1.85, and
1.5<.nu.3/.nu.2 (2)
is satisfied. Moreover, |f1/f23|=1.48, and
0.5<|f1/f23|<3.0 (3)
is satisfied. Moreover, L/f=3.55, and
0<L/f<10.0 (4)
is satisfied. Moreover, N1=1.51, and
N1<1.80 (5)
is satisfied. Moreover, R3/f=0.69, and
R3/f<1.0 (6)
is satisfied. Moreover, D1/f=0.54, and both expressions:
D1/f<1 (7)
0.5<D1/f<0.8 (8)
are satisfied. Moreover, R4/D3=-3.33, and both expressions:
2<|R4/D3|<6 (9)
2.5<|R4/D3|<4.2 (10)
are satisfied. Moreover, (D1+D3+D6)/f=2.15, and both
expressions:
1.5<(D1+D3+D6)/f<4 (11)
2<(D1+D3+D6)/f<3 (12)
are satisfied.
[0054] When the first, second, and third lenses are formed by
plastic, it is possible to realize an imaging lens in which highly
accurate aspherical surfaces can be formed, and which is low in
weight and cost. In the case where plastic is used as the material
of the first lens in a use in which high weather resistance is
requested as in an imaging lens for a vehicle camera, it is
preferable that a coating for improving the acid resistance, the
weather resistance, the water resistance, the strength, and the
like is applied to the object-side surface of the first lens, or
that a protective glass cover is disposed in front of the first
lens. As the protective glass cover, a planar or curved plate
having no refractive power may be used. The use of the imaging lens
of the invention is not restricted to a vehicle camera, and the
imaging lens can be used in a camera apparatus such as a camera for
a portable telephone or a surveillance camera. In a use in which
high weather resistance is requested as in an imaging lens for a
vehicle camera, glass having excellent weather, water, and chemical
resistance properties may be used as the material of the first
lens.
[0055] Although description has been given heretofore of the
invention with reference to the above-mentioned embodiments and
examples, the invention is not limited to such embodiments and
examples but various modifications are also possible. For example,
the values of the radii of curvature, surface intervals and
refractive indexes of the respective lens components are not
limited to the values that are shown in the above-mentioned
numerical examples, but other values can also be used. Also, in the
above-mentioned embodiments and examples, the both surfaces of the
first to fourth lenses are all formed as aspherical surfaces;
however, the invention is not limited to this.
[0056] This application claims foreign priority from Japanese
Patent Application No. 2006-268866, filed Sep. 29, 2006, the entire
disclosure of which is herein incorporated by reference.
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